Evidence of the stabbing to death of an innocent man in Woolwich is smeared in blood all over his suspected attacker's hand, the picture above shows.
In chilling images, a man identified as Michael Adebolajo clutches blood-soaked weapons. He brazenly shows his bloodstained hand to the camera.
Out of shot and a short distance away, his accomplice is telling a bystander why they attacked fusilier Lee Rigby just 400 yards from the perimeter fence of the Royal Artillery Barracks..
According to witness testimonies, the victim was either decapitated or had his head almost chopped off.
The attack was quickly condemned by the Muslim Council of Britain and Islamic groups up and down the country. Prime Minister David Cameron insisted that the United Kingdom would never "buckle" under terrorism.
Unfortunately, ideological attacks are something with which Britons have become wearily familiar over the decades. Yet the killing of Rigby was also startling different from other terror attacks.
Usually, terrorists target crowds of people with bombs calculated to cause maximum carnage and destruction. The Woolwich attack could not have more different.
For the first fatal terror attack on British soil since the London bombings of 2005, they chose tools which turned their plot into close combat. It was more of an assassination than mass murder.
Shaken witnesses spoke in terms of the attackers behaving like butchers carving up meat. It is distressing to think of such a thing happening to someone anywhere - let alone in a nondescript street in multicultural Britain.
The real details will emerge at the trial of Michael Adebolajo and Michael Adenowale. They are in hospital after they were shot by police.
The Telegraph has printed a front-page picture of Adebolajo scuffling with police at a demonstration outside the Old Bailey in 2006. As he was led away, he shouted that he had the right to irge people to "behead those who insult Islam", the Telegraph reported.
The use of sharp weapons and the reported bid to decapitate Rigby recall methods of torture and violence consigned to the Dark Ages.
Many cultures have a history of decapitation. In England, King Henry VIII dispatched two of his wives in this way. A century and a half later, the head of Oliver Cromwell was removed from its resting place and stuck on a spike at London Bridge.
Nowadays in civilised world, beheadings belong in textbooks and films. Yet the practice does persist in certain regions from which al-Qaida emerged.
In the Arabian peninsula, beheading is used by the authorities in Saudi Arabia in certain cases of moral crime. In Iraq, under the secular regime of Saddam Hussein, prostitutes and pimps were beheaded by the state.
During and after the second Iraq war, extremist insurgent groups decapitated hostages as a means of sending powerful statements to their enemies. That fate befell British engineer Kenneth Bigley in Iraq and American journalist Daniel Pearl in Pakistan.
Pearl, a Wall Street Journal reporter, had his throat slit and his head cut off in a videotape made by his captors who were demanding the release of all Muslim prisoners from Guantanamo Bay.
According to the Salafist strain of extremist Islam, the Koran sanctions beheading as punishment for those who have not submitted to Allah.
Under this minority sect's fundamentalist interpretation, there are no innocent non-Muslims because non-believers are guilty of not following the Holy Book.
Similarily, it seems that in the minds of the two Woolwich attackers there are no innocent soldiers. Nursing a grievance over the conflicts in Iraq and Afghanistan, the two men appear to have decided that any soldier is a legitimate target.
If the point of terrorism is to spread terror, then decapitating a victim in the street before dragging the body into the road provides just about the most vivid and dramatic method possible.
It is deeply sad that young father Lee Rigby happened to be in the wrong place at the wrong time when two men decided to bring the Dark Ages back to London's streets.